1. Field of the Invention
The present invention relates to locking devices and more specifically, to a lock cylinder and key set of which the lock cylinder has a dual keyhole type keyway, and the key is a double blade key fitting the keyway of the lock cylinder.
2. Description of the Related Art
FIG. 1A shows a lock cylinder and key set according to the prior art. According to this design, the lock cylinder 10 has a cabinet keyway 14, a plurality of transverse holes 11 respectively perpendicularly disposed in communication with the cabinet keyway 14 in different directions, a -plurality of spring members 12 respectively mounted in the transverse holes 11, and a plurality of pins 13 respectively supported on the spring members 12 and partially projecting into the cabinet keyway 14. The key 1 is a flat blade insertable into the cabinet keyway to act against the pins 13. FIG. 1B shows another design of lock cylinder and key set according to the prior art. This design is substantially similar to the design shown in FIG. 1A with the exception that the keyway, referenced by 15, is a crossed keyway, and the key, referenced by 2, has a blade of 1, crossed cross section. FIG. 1C shows still another design of lock cylinder and key set according to the prior art. This design is substantially similar to the design shown in FIG. 1A with the exception that the keyway, referenced by 16, is a round hole, and the key, referenced by 3, has a cylindrical shank fitting the circular keyway 16.
The aforesaid conventional designs have common drawbacks. One common drawback is that a thief can insert a tool into the cabinet keyway 14, crossed keyway 15 or circular keyway 16 to unlock the lock cylinder 10 easily. Another common drawback is the weak structural strength of the lock cylinder 10. Because the lock cylinder is made of copper and the core (plug) that defines the keyway is cast from zinc aluminum alloy, the lock cylinder can easily be destroyed by a drill.